FI104500B - Process for preparing L-arabinose from sugar beet cut - Google Patents

Abstract

The invention relates to a method of preparing crystalline L-arabinose by extraction of sugar beet pulp, from which sugar has been extracted, in a strong alkaline solution, by hydrolysis of the obtained crude araban with a strong acid at an elevated temperature, by neutralization and filtration of the obtained solution, by chromatographic separation of the L-arabinose fraction, by purification of the obtained L-arabinose solution by means of cation and anion exchangers and adsorbent resins, and by recovering the pure L-arabinose as a crystalline product.

Description

104500

A method for making L-arabinose from sugar beet pulp

The present invention relates to a process for the preparation of crystalline L-arabinose by extraction of a strongly extracted 5 beet sugar beet pulp, hydrolysis of the obtained crude arabic with a strong acid at elevated temperature, separation of the L-arabinose fraction by chromatography, purification of the and recovering pure L-arabinose as a crystalline product. BACKGROUND OF THE INVENTION L-arabinose 10 is prepared from hydrolyzed under acidic conditions from plant materials containing arabinose such as acacia. Another well-known raw material is sugar beet pulp from which sugar has been extracted; of this, L-arabinose has been prepared by hydrolysis under either basic or acidic conditions and purification in several steps. For example, U.S. Patent No. 15,886,078 describes a process for the preparation of L-arabinose from sugar beet pulp by hydrolysis in the presence of lime, filtration and separation of the araban fraction by chromatography; the arabane is then hydrolyzed by addition of acid and the resulting L-arabinose is chromatographed using a Ca-form cation exchange resin. According to one of the previous processes described in GB Application Publication No. 1,182,099, L-arabinose is prepared from beet cut hydrolyzate and separated from the alcoholic solution by crystallization. Invention '; ": It has now been discovered that L-arabinose can be obtained in good yield ·: · *: from sugar beet pulp from which sugar has been extracted simply by: ***: 25 miles under alkaline conditions, by hydrolysis under acidic conditions and · · · separation by chromatography using a monovalent metal (Na +) cation exchange resin as the resin to give a fraction containing L-arabinose, and finally crystallizing L-arabinose from aqueous solution, avoiding the previous multiple separation and purification steps.

DESCRIPTION OF THE INVENTION The present invention relates to a process for the preparation of crystalline L-arabinose, by combining the following steps: a) extraction of a beet pulp from which the sugar has been extracted. (b) hydrolysis of the obtained crude araban with a strong acid at an elevated '···' temperature, 104500 2 (c) neutralization and filtration of the resulting solution, (d) chromatographic separation of the L-arabinose fraction using a monovalent metal resin e) purifying the resulting L-arabinose solution with cation and anion exchangers and adsorbent resins; and f) recovering pure L-arabinose as a crystalline product.

Pure L-arabinose can be prepared by the process of the invention. According to the invention, the sugar beet pulp from which the sugar has been extracted is extracted with a basic solution to dissolve araban. After filtration, the basic extract is hydrolyzed with acid to give a crude L-arabinose solution. The crude arabinose fraction is chromatographed using a cation exchange resin in the form of a monovalent metal (Na +) (e.g., sulfonated polystyrene divinylbenzene; 5.5% DVB) and water as eluent, followed by further purification by ion exchange. The solution is concentrated to about 15% to 70% by weight and crystallized with pure L-arabinose. The crystals are separated by centrifugation and air dried.

The chromatographic separation resin is a sulfonated polystyrene-divinylbenzene (5.5% DVB) in the form of a monovalent metal (Na +, K +). Purification and decolorization are performed with cation-20 and anion exchange resins and other adsorption resins.

Preferably the sugar beet cut stabilized by the biotechnological process according to Finnish Patent Application 973501 is used as starting material. The following is a general process diagram.

25 Sugar Beet Cut • · ·

Aqueous suspension containing about 5-10% solids.

Extraction under basic conditions (for example, Ca (OH) 2 slurry, pH

10-12, 95-100 'C, 4-5h) • · »*; [/ 30 Acid neutralization (pH below about 9) • · · * · * * Filtration • · t

Crude Arabic Solution 35 Evaporation (40-50% by weight)

Hydrolysis (e.g. H 2 SO 4 .90 ° C, pH 0.8) 3 104500

Neutralization (e.g. with NaOH, pH about 6) 5 Crude L-arabinose solution

Filtration (gypsum removal)

Chromatographic separation (for example, Na * form cation exchange resin, 70 ° C) 10 L-arabinose solution

Approximately 10% of dry matter Cation and anion exchange Decolourization 15 Evaporation (approximately 70% by weight)

Crystallization _ ^ Recycling

Drying i 20

Pure L-arabinose Crystals: A preferred embodiment of the invention

According to a preferred embodiment, the beet cut, *; * · I, from which the sugar has been extracted, is suspended in a strongly alkaline solution and. The extract is extracted for 4-5 hours at a pH of about 10-12 and a temperature of 95-100 ° C. The "basic" "solution" is preferably limestone containing 25-40% by weight of Ca (OH) 2 based on the dry matter of the sugar beet pulp. Alternatively, buffered alkaline solutions (KOH, NaOH) may be used. The resulting mixture ... is neutralized to precipitate the calcium salt, for example with carbon dioxide or alternatively sulfuric acid, a suitable pH of about 9 or less. After filtration, the solution is concentrated to about 40% by weight, followed by: hydrolysis under acidic conditions, for example by adding sulfuric acid at a pH of about 0.8. The hydrolysis is carried out at a temperature of about 90 ° C, after which the solution is cooled to about 70 ° C and neutralized by addition of base 35 (e.g. NaOH) until the pH is about 6. The neutralized solution is separated chromatographically using the monovalent metal form, preferably 4 104500 cation exchange resin. The fraction of the separated arabinose-containing fraction has a dry matter content of 5-10%, of which 75-80% is L-arabinose. Pure L-arabinose crystals are obtained by evaporation (about 70 wt% solution), seeding and cooling crystallization. The crystals can be separated by centrifugation.

Another preferred way to extract and hydrolyze araban is to proceed directly with acid hydrolysis after alkaline hydrolysis to cleave araban to L-arabinose. In this embodiment, the alkaline extraction takes about 4-5 hours, after which the pH is adjusted to about 0.8 with sulfuric acid. The extract is treated at 90 ° C until the arabic is cleaved, after which the suspension is neutralized (pH 6), filtered on a suction press and concentrated by evaporation for chromatographic separation.

The choice of method depends on the equipment capacity and the suitability of the raw material.

Example 1 30-40% by weight of calcium hydroxide was added to hot water (95-100 ° C). The dried sugar beet pulp, roughly 0.5 cm in size, from which the sugar was extracted, was suspended in the lime milk thus obtained in a mixture of about 8% by weight, and stirred for 3-4 hours at 95-100 ° C at a pH of 10-12. The mixture was cooled to 75 ° C and neutralized by addition of carbon dioxide until pH 9, whereupon calcium carbonate precipitated. The neutralized mixture was filtered with a filter press.

: The filtrate containing 4% polysaccharides (crude arabinogalactan) was concentrated to 40% by weight by evaporation and sulfuric acid was added at a pH of 0.8. The arabic was hydrolyzed at 90 ° C, then the solution was cooled to 70 ° C and 10% w / w sodium hydroxide solution was added until the pH was 6. The neutralized solution was filtered and the L-arabinose was separated chromatographically using Na +. sulfonated polystyrene • · · divinylbenzene cation exchange resin. The L-arabinose fraction containing 8% of the dry substance (of which 80% was L-arabinose) was recovered. The L-arabinose solution was colored by evaporation and purified by cationic and • · * * · [* anion exchange followed by decolorization with Optipore® (Dovex®) -? * ·: Adsorption resin (manufactured by Dow Chemical, USA). The purified solution was concentrated to 70% by weight, seeded with arabinose crystals and crystallized by cooling to room temperature. The crystals (arabinose purity greater than 98%) were separated by lin-35 coax and dried in a hot air stream. The yield of L-arabinose crystals was 10% by weight based on the dry weight of the pulp.

5 104500

Example 2

A fresh sugar beet slice, roughly 0.5 cm in size, from which the sugar was extracted and pretreated with biotechnological pretreatment (described in Patent Application 973501 and Example 3), was suspended in 5 hot (95-100 ° C) lime milk (30-40% Ca). (OH) 2 from beet cut dry matter) to 7% by weight. The mixture was extracted as in Example 1, the extracted slice was separated from the solution by decantation centrifugation and the crude araban was hydrolyzed as described in Example 1. L-arabinose was separated by chromatography and purified by ion exchangers and decolorized as described in Example 1-10. L-arabinose was crystallized from a concentrated solution in a yield of 15% by weight on a dry basis.

Example 3

Freshly pressed, almost sugar-free beet pulp (22% dry matter) was mixed with '' Ensimax '' (formic acid, acetic acid and lignosulfo-15-sodium mixture, manufactured by Kemira Oy, Finland) until pH 4. The resulting mixture was packed in a sealed container from the air and light. The mixture was allowed to stabilize for one month. Pretreatment removes oxygen and free sugars from the blend, and thus the pre-treated slice is stable for at least one year when stored at non-elevated temperature. The pretreated slice is used as a raw material for the production of L-arabinose.

Example 4: The crude arabinose solution obtained by acid hydrolysis was filtered and chromatographed to purify L-arabinose from the other components.

The separation was carried out on a pilot chromatography column as a batch process using Na + cation exchange resin (manufactured by Finex Oy, Finland); The resin was a sulfonated polystyrene cross-linked (cross-linked) with divinylbenzene; the resin had a degree of crosslinking of 5.5% and an average particle size of 0.35 mm. The inside diameter of the column was 1.0 m and the height of the resin column was about 5.2 m, V30, resulting in a resin volume of about 4000 liters. The separation was carried out at 80 ° C (using a heated column) using deionized water as eluent.

: * · -? The separation process was carried out as follows:

Phase 1:

Approximately 400 liters of arabinose solution (125 kg of dry substance) was passed to 35 columns through a heat exchanger at a flow rate of about 750 l / h. The solution had a dry solids content of 10450000, about 35 g of dry substance per 100 g of solution.

Step 2:

The eluent (deionized water) was passed down the column at a flow rate of 650 L / h. The eluent was also passed through a heat exchanger.

5 Step 3:

According to this information, the solution was divided into two fractions: a residual fraction (containing salts and traces of glucose, galactose and fructose), and an arabinose fraction (containing arabinose and 10 fructose).

A recycling fraction containing glucose, galactose, fructose and a small amount of arabinose can also be recovered between the two fractions. The recycling fraction may be recycled to the column or used to dilute the feed solution.

The amount and composition of dry matter (KA) of arabinose fraction and feed solution are shown in Table 1. The content of components is expressed as weight percent of total dry matter of the fraction. The yield expresses the amount of L-arabinose in the arabinose fraction relative to the total amount of L-arabinose, based on the amounts of L-20 arabinose in both obtained fractions.

v: Table 1. Values and composition of feed solution and arabinose fraction, ':': and yield of L-arabinose _ Feed solution_Arabinose fraction: V: KA in fraction, kg__127.8_39.2_ KA, g / 100 g solution 35.5 9.8

Conductivity, mS / cm_30.9_1.4_4.4_ pH 5.1 4.7

Glucose,% of KA 1.8 0.7 · · · I - - ''

Galactose,% of KA 1.3 2.1 · · * '-

Fructose,% KA.sta__1 ^ 2_2L9_

Arabinosis,% of CA 24.7_77.6_

Arabinose yield,% __96.3_257104500

The arabinose yield is the ratio of the amount of arabinose in the arabinose fraction to the amount of arabinose in the feed solution (%).

Example 5

The crude arabinose solution obtained from the acid hydrolysis was filtered off with a pressure filter and chromatographed on an industrial scale. The separation column used was a conventional batch separation column, 7.0 m high and 2.8 m internal diameter.

The resin used was a Na + cation exchange resin (manufactured by Finex Oy, Finland), the resin was sulfonated polystyrene siliconized with divinylbenzene; the degree of crosslinking was 5.5% and the particle size was about 0.45 mm. The height of the resin column was about 6.4 m and the volume of resin was thus about 38 m3. The temperature in the column and in the feed solution tank was about 70 ° C.

The principle of separation is the same as in Example 1 (steps 1-3). The feed volume was about 2000 liters (780 kg dry matter), i.e. a concentration of 34 15 g / 100 g solution. The flow rate in the column was about 5 m3 / h. Two fractions were recovered as in Example 1. Table 2 shows the dry solids (KA) content and composition of the feed solution and the arabinose fraction.

Table 2. Values and composition of feed solution and arabinose fraction, 20 and yield of L-arabinose '·' '_ Feed solution_Arabinose fraction' 'in KA fraction, kg_ 777__157_: KA, g / 100 g solution_33.9_JM3_ pH __ ^ 5_:. ^ 5_

Galactose,% of KA 2.4_ ^ 5_

Fructose,% of KA__1 ^ 2_ ^ 1_

Arabinosis,% of CA 18.0 80.5 • .....

: 1 · 1: Arabinose yield,% 90.4 • · • · ·

Yield calculated as in the previous example.

. 45 104500

Example 6

40% by weight of calcium hydroxide, based on the dry matter content of the beet cut to be treated, was added to the hot water at about 98 ° C. The dried, almost sugar-free slice was suspended in an alkaline solution to a mixture of about 9 to 5% by weight, and the mixture was stirred for 4 hours at 98 ° C and a pH of about 10. Sulfuric acid was added until pH 0.8 and hydrolyzed at 90 ° C. -arabinose. The suspension was cooled to 70 ° C and 10% w / w sodium hydroxide solution was added until pH 6.0. The neutralized mixture was filtered on a suction press and concentrated to 40% by weight.

The solution was finely filtered on a Seitz filter using diatomaceous earth, after which L-arabinose was separated from the solution by chromatography as in the previous examples. A fraction of L-arabinose having a dry weight of 8% by weight, of which 80% of L-arabinose was recovered. The solution was concentrated by evaporation to 30-15% by weight, purified by cation exchange and anion exchange, and with a decolorization resin (Optipore® / Dovex®), and evaporated to 70% by weight, then the solution was seeded and L-arabinose was crystallized by cooling at room temperature. The purity of the crystals was over 98%. The arabinose yield, calculated on the dry matter of the raw material, was 10%.

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Claims (10)

A process for the preparation of crystalline L-arabinose, characterized in that a combination of the following steps: a) extracting sugar beet slice from which the sugar has been boron extracted with a strongly basic solution; b) hydrolyzing the obtained pure araban c) neutralization of the obtained solution and filtration, d) separation of an L-arabinose fraction chromatographically using as separation resin an ion exchanger in monovalent metal form, e) purification of the obtained L-arabinic solution with the help of cation and anion exchangers and adsorbent resin, and f) utilizing pure L-arabinose as a crystalline product. 15 Process according to claim 1, characterized in that in point a) the extraction is carried out at a pH of 10 -12. Process according to claim 2, characterized in that calcium hydroxide sludge is used as a base. Method according to claim 1, characterized in that at the end of the neutralization, the pH is 6 at 20 c). Process according to claim 4, characterized in that the neutralization is carried out with carbon dioxide or sulfuric acid. Process according to Claim 1, characterized in that in ': "point b) the hydrolysis is carried out at a pH of about 0.8 at a temperature of about 90 ° C. Process according to claim 1, characterized in that in: V: point d) the cation exchanger is in Na + form. Process according to claim 1, characterized in that as a starting material a sugar beet cut stabilized by a biotechnical process is used. I I · 30 Method according to claim 8, characterized in that the stabilized sugar beet cut has a pH of 3.5 - 4.5 (preferably 3.9 - 4.3) and a dry matter content of 20 - 27% by weight. , and the slice is essentially free from fermentable sugars.